1. Field of the Invention
The invention relates to the field of projection television; and more particularly to the use of small portable TV projectors having a liquid crystal light valve to modulate light from a fixed light source. Such projectors are often referred to as LCD projectors, to distinguish them from earlier types having one or more high brightness cathode ray tubes. LCD projectors offer convenience to the user because the projector may be little larger than a 35 mm photographic slide projector, and is therefore portable.
2. Description of the Prior Art
LCD TV projectors are now commercially available, but as a practical matter are limited either to portable use for front projection against a screen or wall, or non-portable use when installed in a rear screen projection TV arrangement.
Particularly in a private home, front projection has the advantage that the picture size can be adjusted to the audience requirements, by using a zoom projection lens or moving the projector closer to or farther from a wall or screen. However, this technique requires that the general room lighting level be undesirably low, so that sufficient picture contrast can be obtained. Further, if reasonable audio fidelity is desired, the projector must use an external loudspeaker system. To cause the sound to seem to come from the vicinity of the picture, the loudspeakers must be placed or moved to a position which may be undesired for other room activity.
Because of the disadvantages of front projection described above, most home TV projection systems use rear projection. This enables easy integration of the TV sound system with the cabinet or wall in which the screen is placed, and provides maximum screen brightness and picture contrast for a given size and power of the light source/valve assembly. However, this system lacks the flexibility of providing a much larger image, even if not so bright, when viewing by a relatively large group is desired.